Abstract: A new method and apparatus have been taught for storing error information used for debugging as generated by the initial and subsequent error occurrences. In this invention, a register with several bit ranges is used to store error information. The first bit-range is allocated to the initial error information. If the total number of the errors exceeds the capacity of the register, the last error is kept in a last bit-range. This way, precious initial error information (as well as the last error information) will be available for debugging.

Abstract: A new method and apparatus have been taught for storing error information used for debugging as generated by the initial and subsequent error occurrences. In this invention, a register with several bit ranges is used to store error information. The first bit-range is allocated to the initial error information. If the total number of the errors exceeds the capacity of the register, the last error is kept in a last bit-range. This way, precious initial error information (as well as the last error information) will be available for debugging.

Abstract: A computer which has multiple central processing units where at least one of the processors is a spare and unused for normal system operation, provides a mechanism for transferring the micro-architected state of a checkstopped processor to a spare processor. Each processor has a set of registers in the central processing unit where the micro-architected state of the processor is kept and these registers are accessible by millicode or microcode running on that processor. A checkstop of a processor is detected by the system, the micro-architected state of that processor is extracted and returned to the system where that state can be loaded into a spare processor in the system and processing resumed without interruption.

Abstract: A computer processor which has a apparatus in its Execution Unit (E-unit) that detects a match between an opcode about to be executed and opcodes programmed into it by the computer manufacturer provides a method for alleviating design deficiencies in the processor. The E-unit further contains a mechanism for transmitting the opcode and a desired action back to the Instruction Unit (I-unit) where it may be compared with the next instruction that is decoded. Furthermore, the E-unit opcode compare logic contains a mechanism for breaking infinite loops that may result. This E-unit opcode compare mechanism, may also be used for other purposes such as detecting invalid opcodes and other exception checking since it may allow for a faster cycle time of the processor than if this logic were implemented in the I-unit.

Abstract: A millimode capable computer system provides control to millicode to allow the BHT operations to continue except when the these special situations occur that require control of instruction fetch operations must be provided and the BHT can be turned off for some sections of code execution, but not disabled for all. A single free running BHT functions for both a normal mode and a millimode for the central processor which can execute in millimode with a branch history table directing instruction fetch for which both a global BHT disable and millicode disables exist. Hit detection logic receives input from the global BHT disable, as well as from an initialized control register bit and a processor control register bit to select the correct set target information and generate a "branch history table hit detected" control signal.

Abstract: A pipelined multiprocessor system for ESA/390 operations which executes a simple instruction set in a hardware controlled execution unit and executes a complex instruction set in a milli-mode architected state with a millicode sequence of simple instructions in the hardware controlled execution unit, comprising a plurality of CPU processors each of which is part of said multiprocessing system and capable of generating and responding to a quiesce request, and controls for system operations which allow the CPUs in the ESA/390 system to process the local buffer update portion of IPTE and SSKE operations without waiting for all other processors to reach an interruptible point, and then to continue program execution with minor temporary restrictions on operations until the IPTE or SSKE operation is globally completed. In addition, Licensed Internal Code (LIC) sequences are defined which allow these IPTE and SSKE operations to co-exist with other operations which require conventional system quiescing (i.e.

Abstract: A computer which has multiple central processing units where at least one of the processors is a spare and unused for normal system operation, provides a mechanism for transferring the micro-architected state of a checkstopped processor to a spare processor. Each processor has a set of registers in the central processing unit where the micro-architected state of the processor is kept and these registers are accessible by millicode or microcode running on that processor. A checkstop of a processor is detected by the system, the micro-architected state of that processor is extracted and returned to the system where that state can be loaded into a spare processor in the system and processing resumed without interruption.

Abstract: A millimode capable computer system provides control to millicode to allow the BHT operations to continue except when the these special situations occur that require control of instruction fetch operations must be provided and the BHT can be turned off for some sections of code execution, but not disabled for all. A single free running BHT functions for both a normal mode and a millimode for the central processor which can execute in millimode with a branch history table directing instruction fetch for which both a global BHT disable and millicode disables exist. Hit detection logic receives input from the global BHT disable, as well as from an initialized control register bit and a processor control register bit to select the correct set target information and generate a "branch history table hit detected" control signal.

Abstract: A computer processor floating point processor six cycle pipeline system where instruction text is fetched prior to the first cycle and decoded during the first cycle for the fetched particular instruction and the base (B) and index (X) register values are read for use in address generation. RXE Instructions are of the RX-type but extended by placing the extension of the operation code beyond the first four bytes of the instruction format and to assign the operation codes in such a way that the machine may determine the exact format from the first 8 bits of the operation code alone.

Abstract: SMP computers systems can add to the first level cache a fill mode latch and achieve straightforward, high-performance loading of a writable cache code array that is part of a hierarchical cache structure.A new code array's write control elements include a control latch called "fill mode" for the BCE controls which when fill mode is active, then a disable is also active, since reads of the code array may not give accurate data when the array is not yet filled-up/fully valid. New mode follows the sequential steps which process code by:a) purge the cache array; thenb) disable the code array; thenc) turn on fill mode with a buffer control element fill mode latch; and then processd) code increments once through a range of line addresses, where the range is at least as wide as the range(s) specified in the code array's lookup mechanism.e) turn off fill mode; thenf) purge the cache array again: and theng) enable the code array (turn off the code array disable bit).h) resume normal operation to end the sequence.

Abstract: A computer processor which has an apparatus in its Execution Unit (E-unit) that detects a match between an opcode about to be executed and opcodes programmed into it by the computer manufacturer provides a method for alleviating design deficiencies in the processor. The E-unit further contains a mechanism for transmitting the opcode and a desired action back to the Instruction Unit (I-unit) where it may be compared with the next instruction that is decoded. Furthermore, the E-unit opcode compare logic contains a mechanism for breaking infinite loops that may result. This E-unit opcode compare mechanism, may also be used for other purposes such as detecting invalid opcodes and other exception checking since it may allow for a faster cycle time of the processor than if this logic were implemented in the I-unit.

Abstract: A computer processor that allows the execution of the IBM ESA/390 STOSM and STNSM instructions, in an overlapped fashion, contains an apparatus that allows the STOSM and STNSM instructions to be executed without serializing the processor, or otherwise delaying subsequent instructions, after the STOSM or STNSM instruction, in most cases, thereby improving performance. It contains a mechanism that counts cycles after their execution and prohibits asynchronous interrupts during that time. The invention also contains an efficient mechanism for handling the execution of the STOSM and STNSM instructions when the processor is executing in the SIE environment.

Abstract: A computer processor that allows the execution of the IBM ESA/390 SPKA instruction, in an overlapped fashion, contains an apparatus that allows the SPKA instruction to be executed without serializing the processor after its execution in most cases, thereby improving performance. It contains a mechanism in the processor's cache that monitors if the Fetch Protect bit in the storage key is on, for instruction data being fetched. It also contains a mechanism to remember if an SPKA instruction has been executed recently. Based on this information, an apparatus determines if it really must serialize the processor after execution of the SPKA instruction.

Abstract: A computer processor system having a floating point processor for instructions which are processed in a six cycle pipeline, in which prior to the first cycle of the pipeline an instruction text is fetched, and during the first cycle for the fetched particular instruction it is decoded and the base (B) and index (X) register values are read for use in address generation. Instructions of the RX-type are extended by placing the extension of the operation code beyond the first four bytes of the instruction format and to assign the operation codes in such a way that the machine may determine from the first 8 bits of the operation code alone, the exact format of the instruction. Instructions formats include the ESA/390 instructions SS, RR; RX; S; RRE; RI: and the new RXE instructions. where instructions of the RXE format have their R.sub.1, X.sub.2, B.sub.2, and D.sub.

Abstract: A pipelined multiprocessor system for ESA/390 operations which executes a simple instruction set in a hardware controlled execution unit and executes a complex instruction set in a milli-mode architected state with a millicode sequence of simple instructions in the hardware controlled execution unit, comprising a plurality of CPU processors each of which is part of said multiprocessing system and capable of generating and responding to a quiesce request, and controls for system operations which allow the CPUs in the ESA/390 system to process the local buffer update portion of IPTE and SSKE operations without waiting for all other processors to reach an interruptible point, and then to continue program execution with minor temporary restrictions on operations until the IPTE or SSKE operation is globally completed. In addition, Licensed Internal Code (LIC) sequences are defined which allow these IPTE and SSKE operations to co-exist with other operations which require conventional system quiescing (i.e.

Abstract: A computer system having a pipelined computer processor, which executes a relatively simple instruction set in a hardware controlled execution unit and executes a relatively complex instruction set in a milli-mode architected state with a millicode sequence of simple instructions in said hardware controlled execution unit, a millicode operating in a milli-mode state when macro-mode decoding by said processor is suspended to cause the system to subsequently use processor milli-registers and the processor's decoder decodes them and schedules them for execution upon entry into the processor milli-mode. Millicode flags allow specialized update and branch instructions and flags are either cleared or specifically set for a millicode instruction. A millicode instruction for editing functions processes one byte of an input pattern string, generates one byte of an output string, and updates various pointers and state indications to prepare for processing the next byte in a string.

Abstract: IEEE compliant floating point unit mechanism allows variability in the execution of floating point operations according to the IEEE 754 standard and allowing variability of the standard to co-exist in hardware or in the combination of hardware and millicode. The FPU has a detector of special conditions which dynamically detects an event that the hardware execution of an IEEE compliant Binary Floating Point instruction will require millicode emulation. The complete set of events which millicode may emulate are predetermined early in the design process of the hardware. An exception handling unit assist millicode emulation by trapping the result of an exceptional condition without invoking the trap handler. When an exceptional condition is detected during execution, the IEEE 754 standard requires two different actions under control of a mask bit. If the mask bit is on, the result is written into an FPR and the trap handler is invoked.

Abstract: Computer system element has a VLSI array with redundant areas and an ABIST (Array Built-In Self Test) system having mirror image fuse registers enabling scan of failed addresses to be used to replace hardware errors detected during power-on at a customer location. The ABIST controller allows self test functions (e.g. test patterns, read/write access, and test sequences) to be modified without hardware changes to the test logic. Test sequence is controlled by logical test vectors, which can be changed, making the task of developing complex testing sequences relatively easy and useful for enabling array self-tests to be performed in a customer's office at power-on reset.

Abstract: Computer system element has a VLSI array with redundant areas and an ABIST (Array Built-In Self Test) system having mirror image fuse registers enabling scan of failed addresses to be used to replace hardware errors detected during power-on at a customer location. The ABIST controller allows self test functions (e.g. test patterns, read/write access, and test sequences) to be modified without hardware changes to the test logic. Test sequence is controlled by logical test vectors, which can be changed, making the task of developing complex testing sequences relatively easy and useful for enabling array self-tests to be performed in a customer's office at power-on reset.